This invention relates to a roll feed device in which a sheet-like material is held between and fed by a main roll and a sub-roll.
For example, in a cutting machine for cutting a material into a predetermined length or a pressing machine, used in a factory automation system, a sheet-like metal material is intermittently fed by a roll feed device from a roll of such material, and the sheet-like material thus fed is cut or pressed each time the roll feed device stops feeding the material.
Generally, such a conventional roll feed device includes an electric motor as a drive source, and the rotation of the motor is transmitted to a main roll of the roll feed device via intermediate transmitting elements such as a belt, gears, joints and so on. The roll feed device comprises the main roll and a sub-roll disposed in opposed relation to the main roll, and a gap between the main roll and the sub-roll is adjusted according to the thickness of the sheet-like material to be fed therebetween, and is so determined that the main roll and the sub-roll are slightly pressed against the sheet-like material. With this construction, the main roll is driven for rotation, and the sheet-like material is supplied between the main roll and the sub-roll, so that the sheet-like material is fed by the friction between the main roll and the sheet-like material. At this time, the sub-roll is rotated in response to the movement of the sheet-like material.
In such a conventional roll feed device, however, since the rotation of the motor is transmitted to the main roll via the intermediate transmitting elements such as a belt, gear, joints and so on as described above, rattling, backlashes, vibrations and the like, develop in the intermediate transmitting elements. This has resulted in a problem that the uniformity of the feed speed and the positioning accuracy or precision can not be satisfactory. Another problem is that the device tends to be bulky because of the intermediate transmitting elements.